In playing the game of baseball, a competent player must be able to field well and be a good batter against first class pitching. A first class pitcher can throw straight balls of varying speeds and curve balls which curve or "break" to a greater or less degree depending upon the speed and twist imparted to the ball.
In throwing straight balls, the stress on the pitcher's arm is far less than that imposed when throwing a curve. The curve requires, in addition to the usual throwing motion of the arm, a rapid twisting movement of the hand, wrist, forearm, and elbow just before release of the ball.
Repeated throwing of curves puts so much stress on the pitcher's wrist and elbow that a "sore arm" is very likely to develop. Under game conditions, a pitcher will mix up his curves and straight balls to make it as difficult as possible for the batter to hit the ball. Under practice conditions, however, coaches at all levels (little leagues through major leagues) are reluctant to call on their pitchers to throw many curves to practicing batsmen lest the pitchers be incapacitated by the development of "sore arms."
Therefore, the batter's opportunities to practice hitting curve balls are limited with the result that under game conditions, a good curve ball pitcher usually has the upper hand over the batters.
Attempts have been made to provide mechanical ball throwers capable of throwing curves. These machines, however, are beyond the financial reach of most schools and colleges where most baseball players receive their initial instruction and playing opportunities. Accordingly, the inability to practice at length against curve ball pitching has proved to be a great disadvantage in the development of competent batsmen who in the professional field must be able to hit all kinds of pitches.
A further disadvantage of the mechanical ball thrower is that it does not present to the batter the image of a pitcher winding up and throwing what the batter sees under game conditions.
There is, therefore, a great need for a practice baseball which can be made to curve by an ordinary pitcher without placing any more stress on the pitching arm than that required to throw a straight ball.
We are aware that projectiles or other devices intended to curve when thrown are disclosed in the prior art. See for example the game Projectiles shown in the U.S. patents, to Randall Nos. 3,099,450 and 3,416,800, the light weight Throwing Device of Watson No. 3,930,650, the off center Baseball of Senn No. 1,873,221, and the hollow, light weight Game Ball of Blamey, Jr. et al. No. 2,776,139. However, we are unaware of any ball or throwable device having a size and weight that give it recognition as usable in playing the game of baseball, which when thrown in the way that a straight ball is thrown can be made to curve in a controllable manner.